X-ray tube and x-ray screen supporting structure



Nov. 5, 1935. I o. w. LANGHANS 2,019,612

X-RAY TUBE AND X-RAY SCREEN SUPPORTING STRUCTURE Filed Dec. 1, 1953 INVENTOR 0. 14/. Z/l/VV/A/VS ATTORNEY Patented Nov. 5, 1935 UNITE SATES X-RAY TUBE AND X-RAY SCREEN SUPPORTING STRUCTURE Otto W. Langhans, Bloomfield, N. 3., assignor to Westinghouse Lamp Company,

of Pennsylvania a corporation Application December 1, 1933, Serial No. 700,412

5 Claims.

This invention relates to electric discharge devices and more particularly to X-ray tubes. In its more specific aspect the invention is directed to an X-ray shield and means for supporting the same.

Prior to my invention, it has been proposed to construct X-ray tubes including an anode and a cathode with an X-ray screening means. The X-ray screening means may be supported by an upwardly extending reentrant tube extending along the longitudinal axis of the tube in the manner disclosed by Clayton T. Ulrey in his United States Patent 1,872,335 dated August 16, 1932 or by means of resilient plates bearing against both the interior surface of the envelope and the exterior of the screen as disclosed by Nelson H. Stewart in his United States Patent 1,920,606 dated August 1, 1933.

My improved X-ray tube is so designed that neither of the aforementioned means of supporting my X-ray screen may be employed. I have devised an improved X-ray screen and a novel means for supporting the same. In its briefest aspect the invention is directed to an X-ray screen which may be of cylindrical form and has its edge so constituted that no corona discharge will take place thereat and there is provided a support associated with the screen and a stem of the tube to maintain the screen in fixed position.

An object of my invention is to provide an X-ray tube whose X-ray screen may be readily manufactured and which is not subject to corona discharge effects during the operation of the tube.

Another object of my invention is to provide a simple and novel supporting means for an X-ray screen, with the construction of the supporting means being such that the screen may be quickly assembled.

These and other objects of my invention will be apparent from the following description and drawing wherein,

Figure 1 represents a fragmentary View with the envelope in cross section and the other parts in elevation of an X-ray tube embodying my invention;

Figure 2 represents a cross sectional view taken on line IIII of Figure 4 in the direction of the arrows;

Figure 3 represents a cross-sectional view taken on line TIL-III of Figure 1;

Figure 4 represents a cross-sectional view taken on line IV-IV of Figure 1.

Although I shall hereinafter describe my invention with respect to a low power X-ray tube as for example a dental X-ray tube, it is not to be limited thereby. In addition, the lower end of the X-ray tube embodying a reentrant tube with an anode-supporting and shock-absorbing means is not essential to a complete understanding of my invention. Therefore, I shall describe only 5 the upper portion of the Y-ray tube embodying my invention.

Figure 1 discloses the upper portion of my X-ray tube including a vitreous envelope l0 that is air-tight and preferably highly evacuated. 10 The upper portion l l of the envelope is somewhat bulbous and has an outwardly extending arm it.

A tubular reentrant stem 53 extends into said arm l2 and measures in length just slightly more than the arm l2.

The major portion of the stem I3 is spaced from the arm l2. The stem l3 terminates in a rearwardly extending press M which is surrounded by and located in the cylindrical portion of the major portion of the stem I3. A plurality 20 of leading-in conductors l6 and H are sealed in said press It and extend exteriorly and interiorly of the envelope. The outer end of the arm l2 has a contact cap l8 secured thereto by an appropriate basing cement and the leading-in con- 25 ductors l6 and H are appropriately secured thereto.

Located in said envelope are an anode i9, a cathode 20, an X-ray screening means 2! and a screen supporting means 22. The anode l9 has a free end in which is located a target 23 composed of tungsten or the like material which has good X-ray emitting properties when electrons strike the same. The X-ray screen M is located in the upper portion H of the envelope and has its central longitudinal axis approximately coincident with the central longitudinal axis of the envelope with no part of the screen contacting the envelope. The screen 2| is composed of iron, nickel, nickel-iron, molybdenum or the like and is manufactured by spinning a thin plate of the metal to be employed. The screen 2! simulates an inverted cup with a cylindrical body portion 26, a bottom 25, that portion uniting the bottom 25 and cylinder 2% being arouate and smooth to obviate the danger of corona discharge effects. The lower end 26 of the cup is curved inwardly with the lower edge thereof being closely adjacent the inner surface of the cylinder 24.

This curled lower end 26 is an arcuate rim whereby the potential gradient thereat is so low that cold emission of electrons thereat is precluded. The bottom 25 of said cup has an opening 21 therein located at about the center of said bottom, with the diameter of said opening being suificient to allow the passage therethrough of the useful X-rays generated at the target 23. The rim of said opening is in the form of a curl 28 which is spun edge curled upwardly and around to the upper face of the bottom of the cup and closely contiguous therewith to eliminate the danger of corona discharge thereat.

'A cathode structure consisting of a focusing cup 29 and a spiral filament 30 is mounted in the cup. The focusing cup 29 is adjacent the bottom 25 of the cup and is held in position thereat by screws 3| passing through the opening in the bottom 25 and cooperating with threaded openings in the focusing cup. The filament 30 has one end welded to said cup which is electrically connected to the screen 2| and its other end is electrically connected to a conductor 32 extending through insulator bushing 33 carried by the cup 29 and passing through an opening in the upper end of the cylinder 24. The leading-in conductor I6 is electrically connected to the conductor 32 and to the side of the filament 30 and the leading-in conductor I1 is electrically connected to the screen supporting means 22 through the screen 2| and the focusing cup 29 to the other side of the filament 30. The screen 2| has an indentation in the form of a band around the circumference thereof adapted to accommodate a flexible narrow band 34 of the same composition as the screen 2|. The edges of the band 34 are preferably rounded to prevent corona discharge thereat. The depth and width of the indentations are so chosen that the band 34 may flt therein with its sides substantially flush with the outer surface of the cylinder 24.

The band 34, another flexible band 35, a nut and bolt arrangement 36 and a spacer 3'! constitute the supporting means 22. The band 34 is wrapped around the cylinder and located in the indentation thereof. One portion of said band is in the form of two parallel straight arms between which and near to the cylinder 24 is located the spacer 31. Screws pas through the arms and engage threads on the inner surface of the spacer 37 which is tapped. The spacer 31, together with the screw arrangement, maintains the band tightly around the cylinder. The arms of said band 34 are welded to the comparatively wide metallic flexible band 35 which is wrapped around the reentrant stem l3 and secured thereto by the nut and bolt arrangement 36 so that band 35 is securely clamped in position.

A flexible conductor 38 is electrically connected by welding to the leading-in conductor l1 and to one of the arms of the band 34 whereby the potential of the screen 2| and the focusing cup 29 may be the same as that of said conductor.

With a construction of the type hereinbefore described, I have provided an X-ray tube whose X-ray screening means is not subject to corona discharge and which may be readily assembled in a rugged and simple structure.

It is obvious that changes within the scope of my invention may be made and, therefore, I do not limit myself to the exact construction shown but only to the prior art.

What is claimed is:

1. An X-ray tube comprising an envelope, an anode, a cathode and a screening means therein, said envelope having an outwardly extending arm, a reentrant stem carried by said arm, said stem terminating in a press, means for supporting said screening means by said stem, said means including a clamp encircling said stem, said clamp being removably secured to said stem, means encircling and secured to said screening means, said means being secured to said clamp.

2. An X-ray tube comprising an envelope, an anode, a cathode and an X-ray screening means therein, said envelope having an outwardly extending arm, a tubular reentrant stem terminating in a press, said press being located in the tubular portion of said stem, a removable clamp secured to said tubular stem, and means clamped to said screening means and secured to said removable clamp for supporting said screening means.

3. An X-ray tube comprising an envelope, an anode, a cathode, and an X-ray screening means therein, said envelope having an outwardly extending arm, a reentrant tubular stem carried by said arm, said reentrant tubular stem terminating in a press, said screening means having an indentation in the surface thereof, a flexible means having a portion thereof located in said indentation and gripping said screening means, another portion of said means extending towards said stem, means secured to said stem and to said last mentioned portion and cooperating therewith and with said stem for supporting said screening means.

4. An X-ray tube comprising an envelope, an anode, a cathode and an X-ray screening means therein, said envelope having an outwardly extending arm, a tubular reentrant tube carried by said arm and terminating in a press, said press being located in the tubular portion of said tube, a removable clamp secured to said tubular reentrant tube, another removable clamp having its ends secured to said first mentioned clamp, said screening means having an indentation in the surface thereof, said second mentioned clamp being located in said indentation for gripping said screening means.

50 5. An X-ray tube comprising an envelope, an

anode therein, said anode having a target at one end thereof, an X-ray screening means in said envelope and surrounding said target, said screening means having an opening therein through which X-rays generated at the target may emerge, said envelope having an outwardly extending arm, a reentrant tubular stem carried by said arm and terminating in a press, a cathode carried by said screen, conductors sealed in said press and electrically connected to said cathode, a removable clamp encircling said stem, a removable clamp encircling said screen, said clamps being connected to each other.

O'I'IO W. LANGHANS. 

